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Mathematics Senior High

付箋の部分の計算が分かりません。詳しく解説お願いします🙇‍♀️

例 が特別な数列になっていないか考えてみるとよい。 次の数列の一般項 α を求めよ. XL 1, 7, 17, 31, 49, 71, X(2) 2, 3, 5, 9, 17, 3390 考え方 等差数列や等比数列でないなど, 与えられた数列の規則がわかりにくいとき,各項の から {an} as, a2, a3, aA, a5, ......, an-1, an, 手順で行う (芋) {6} 61, b2, b3, b₁, 数列{bm} を {an} の階差数列という. 2 のとき, 1 n-1 a,=a,+(b,+b2+bs+………+=+20 解答 与えられた数列{a} の階差数列を {bm} とする. 1枚 右にあるカードから1 (1){a}:1, 7, 17, 31, 49,71,=b {bm} : 6, 10, 14, 18, 22, =b2 となり,数列{bm} は,初項6,公差4の等差数列になっ ているから,第ん項 b [k] は, bk=6+(k-1)・4=4k+2 したがって,n≧2 のとき www n-1 n-1 (スタート) an a+b=1+Σ(4k+2) k=1 k=1 =1+4•—(n−1)·n+2(n−1)=2n²−1 2 この式は,n=1 のとき, a1=2・1°-1=1 となり、 +an-ab an-a-Σb より注意! an=a+b k=1 n=1のときのチェ a=1 だから, n=1のときも成り立つクをする。 よって, an=2n²-1 SI (2){a}:2, 3, 5, 9, 17. {6}:1.2. 4. 8, 4,8 となり, 数列{6} は, 初項 1. 公比2の等比数列にな っているから、第ん項bk は, bk=1.2k-12-1 したがって, n≧2 のとき www n-1 12 an=a+bk=2+21=2+ k=1 k=1 2-1 よって、 =2"-'+1 1 この式は, n=1のとき, a=2+1=2 となり, は、a=2 だから, n=1のときも成り立つあり、結果は よって, an=2" '+1 Focus 注意! an=a+Σb k=1 等比数列の和 n=1のときのチ をする.

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English Senior High

この3つが分かりません。教えてください🙇‍♀️

wal Rainforest trees are used to make things which we use every day. Rubber, for example, is used to make many things. The fruits of many forest trees ( 7 ) — forest people have eaten them for thousands of years. Today, all over the world, people eat rainforest food plants; for example, coffee, tea, oranges, and rice. Corn, which is an important food for many people of the world, is another rainforest plant. In 1970, a disease destroyed half the corn in the United States of America. Scientists began to look for new species in the rainforests. In 1987, in the Mexican rainforest, they found a new species which is stronger than other species. But we nearly lost this new species, because people were already cutting down that part of the Mexican rainforest. Hollywood, Los Angele movie stud (1) knows how many useful plants are already lost because people have SHOULD destroyed many of the rainforests of the world. Directors, actors, and writ The trees of the rainforests help the Earth's air because their leaves use carbon dioxide and make oxygen, which we need to live. its high point in these year They are also important because they control some of the Earth's weather. Through they give out water vapor which makes heavy clouds. The clouds then move to other parts of the Earth and give rain. The clouds also protect the Earth their large leaves, from the sun. (ウ) 日 moved to like Today, the Earth is slowly getting hotter, and in some places changes in the weather are making life much more difficult. We need to learn more about the Earth's weather while we still have the rainforests. and see the golden

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